This is Steven Salzberg's blog on genomics, pseudoscience, medical breakthroughs, higher education, and other topics, including skepticism about unscientific medical practices. Here's where I can say what I really think about abuses and distortions of science, wherever I see them.

A new study in the journal Health Affairs looked in great detail at prescription drug usage in U.S. states that have legalized medical marijuana. Researchers Ashley Bradford and David Bradford collected Medicare data for the period 2010-2013 to answer two questions: are patients choosing marijuana instead of prescription drugs for conditions that marijuana might treat, and what has been the overall effect on Medicare spending?

The bottom line: in 2013 alone, when 17 states had legalized medical marijuana, Medicare saved over $165 million. A simple extrapolation suggests that if all states legalize marijuana, annual savings could be triple that amount, $500 million. (Obviously this extrapolation is over-simplified: it depends on the actual populations of those 17 states, and it only considers Medicare. Commercial healthcare plans may save far more.)

The authors, a father-daughter team at the University of Georgia, looked at over 87 million prescriptions from the Medicare Part D database, focusing only on conditions where marijuana "might serve as an alternative treatment." These fall into nine specific categories for which at least some evidence suggests marijuana could help: anxiety, depression, glaucoma, nausea, pain, psychosis, seizures, sleep disorders and spasticity. The best clinical evidence of marijuana's benefits, according to the study, is for pain, for which the clinical evidence is "moderate"; most of the other conditions have evidence rated as low or very low.

Prescriptions fell for 8 out of 9 categories, with the biggest drop occurring for pain medication: in states with medical marijuana laws, physicians gave out 3645 fewer pain prescriptions per doctor, a difference that is highly statistically significant. Or, in raw numbers, the annual number of daily doses (in 2010-2013) per doctor in states without medical marijuana laws was 31,810. In states with medical marijuana, the number dropped to 28,165. That's an 11.5% drop. Depression and seizures both showed very significant reductions in prescriptions as well.

Prescriptions rose for only one condition: glaucoma. This too was expected–as the article explains,

"Clinical evidence is very strong that while marijuana sharply reduces intraocular pressure, the effect lasts only about an hour. As a result, new patients who seek glaucoma treatment after learning about the potential benefits of marijuana are likely to receive a prescription for an FDA-approved drug."

In an interview posted on the University of Georgia website, study co-author David Bradford states that they also wanted to know if medical marijuana laws were just a backdoor way to allow recreational marijuana use, or if people were really using it as medicine. He continues:

"What our evidence is suggesting is that ... there is a significant amount of actual clinical use at work here."

As of today, 24 states have medical marijuana laws on the books. This new study suggests that legalizing marijuana in all states would save hundreds of millions of dollars in Medicare costs, and even more money for people not covered by Medicare–not to mention the savings from no longer wasting law enforcement resources prosecuting marijuana use.

Opponents of legalization have argued since the 1930's that marijuana is a "gateway drug" that will lead to more serious drug abuse and that it increases criminal behavior, without (as Bradford and Bradford point out) any good evidence proving these links. This new study now provides a strong financial argument for legalization: legalizing marijuana, at least for medical use, will yield substantial savings for our health care system.

In recent years, though, they have adopted as one of their causes a rigidly inflexible opposition to all genetically modified foods, a stance that has no basis in science and that threatens to block technology that has great potential for good.

This past Thursday, a group of 110 Nobel Laureates released a letter excoriating Greenpeace for its long-term campaign against genetically modified organisms (GMOs) and especially against “golden rice.” The Nobelists' letter points out that science has shown that GM foods are just as safe and healthy as any other foods, and that Golden Rice has the potential to relieve a great deal of human suffering.

Unfortunately, anti-GMO activists at Greenpeace and elsewhere are ignoring the science. Their opposition seems to rely on two arguments, both of them superficially appealing, but both wrong.

First, there's the argument that "natural" is always better, whether it be applied to your food or to other aspects of life. Many people find this idea very compelling; after all, we humans are part of nature, so why not consume foods in their natural state? This argument is wrong for many, many reasons, far too many to list here, but I'll just mention a couple. We can start with cooking: it sure isn't natural, but cooking allows us to extract far more nutrients from our food, and is one of humankind's greatest inventions. Or consider pasteurization, an unnatural process that has saved countless millions of people from death by killing the bacteria that are present in purely "natural" milk and other products.

Suffice it to say that there's nothing wrong with modifying our food to make it easier to digest, healthier (as with Golden Rice), or just tastier. The fact that some genetic modifications fail to do any of these things doesn't make GMOs bad, it just means that GM technology can be applied in other ways.

The other argument against GMOs, perhaps the more emotional one, is that they're just a stealth method to allow big agricultural corporations to sell more herbicides and pesticides. This isn't exactly wrong: Monsanto's RoundUp Ready® crops are engineered to allow farmers to use more of the herbicide glyphosphate. Regardless of the arguments about herbicides, the fundamental problem with this argument is that it's a gross over-generalization: just because you don't like RoundUp Ready® soybeans doesn't mean that all GMOs should be banned. As the National Academy of Sciences concluded in a report published earlier this year,

"it is the product, not the process, that should be regulated."

Greenpeace, pay attention. That same NAS report also concluded that GM foods are generally safe and just as healthy as non-GM foods.

Now consider Golden Rice, a variety of rice that has been genetically modified so that it naturally produces beta carotene, which humans metabolize to produce vitamin A. Golden Rice has the potential to reduce vitamin A deficiency, which has devastating effects in parts of the world where children struggle to get enough nutrition. As the Nobel Laureates' letter points out, vitamin A deficiency affects 250 million people worldwide, and

"Vitamin A deficiency is the leading cause of childhood blindness globally affecting 250,000 - 500,000 children each year. Half die within 12 months of losing their eyesight."

How could Greenpeace oppose something that could eliminate so much suffering? I can only conclude that the anti-GMO forces within Greenpeace are so consumed by their rigid opposition that they simply cannot see that GMO technology has the potential for great benefits.

Hmm. Neither of these arguments stands up to even a tiny bit of scrutiny. First, even if Golden Rice isn't ready for prime time, it's still a great idea. Would Greenpeace support Golden Rice if it were ready to be shipped to hungry children today? They don't say. And both GMWatch and Greenpeace fail to mention (or deny) the fact that one of the major reasons that Golden Rice isn't yet on the market is that anti-GMO groups have worked very hard to block it, lobbying hard for regulatory barriers and even ripping up a test field.

Second, the argument about relevant expertise is ridiculous. Sir Richard Roberts and Dr. Phillip Sharp, two of the Nobel Laureates who spearheaded the effort to write the letter, are among the world's leading geneticists and molecular biologists, as are many of the other Nobelists who signed the letter. I also have to point out that this is a classic ad hominem attack: rather than address the actual topic, GMWatch are attacking the messengers. (Also, somewhat bizarrely, GMWatch contradicts its own argument in an update they posted to their own article. In the update, they write that "[Dr. Phillip] Sharp is a biotech entrepreneur with interests in GMO research," essentially acknowledging that he is an expert in GMO technology.)

Ad hominem attacks may be entertaining, but they fail to support the Greenpeace argument that GMOs should be banned. Nowhere in GMWatch's article, or in Greenpeace's anti-GMO policy, is there any comment about the extensive scientific evidence that shows that GM foods are safe. As I've written before, you're far more likely to be harmed by being hit on the head by a corn cob than by some kind of deviant GMO corn gene.

I asked Sir Richard Roberts if he had any response to the arguments from Greenpeace, and he replied that:

“Greenpeace just reiterate the old arguments that are adequately debunked elsewhere. Why won't they just admit they got this issue wrong? Is it because they have consistently introduced roadblocks and then wonder why it is taking so long to introduce Golden Rice to the market? Are they serious?”

Greenpeace would do well to reconsider their position, as Dr. Roberts and his colleagues argue. They are flat wrong on the science of GMOs, and their dogmaticism is losing them the support of many scientists (and others) who are strong backers of Greenpeace's other causes. For example, Greenpeace's website features their "Save the heart of the Amazon" campaign, an admirable effort to protect a large swath of the Brazilian rainforest. They also have a major campaign to save the Arctic, a cause I support even more enthusiastically.

One last note: organic food stores, led (in the U.S.) by Whole Foods, have been eagerly promoting the "non-genetically modified" nature of their foods, and pushing for laws to require that all GM foods be labelled. First, I have to point out that this is nonsense. Virtually everything you eat has had its genes modified from their natural state, through centuries of breeding by farmers. The only difference with modern GM food is that we can precisely select the genetic changes we want, unlike the slow, incredibly inefficient methods of traditional agriculture.

Ironically (and this is delicious in more ways than one), Whole Foods does sell massive quantities of one GMO: sweet potatoes. It turns out that all sweet potatoes contain bacterial genes! As Tina Kyndt, Dora Quispe and colleagues reported last year, 291 different varieties of sweet potato all contain genes from a bacterium called Agrobacterium tumefaciens. This bacterium has the ability to insert bits of its own genome into its host, and it did exactly that to sweet potatoes sometime in the recent past, after humans started cultivating sweet potatoes (wild relatives don't have the foreign genes). Apparently, ancient human farmers preferred the sweet potatoes with the bacterial genes, and these were passed on to all modern varieties. So sweet potatoes are not only genetically modified, but they are transgenic: they contains genes from a completely different species.

I was at Whole Foods today, and I failed to notice any labels revealing that their sweet potatoes are transgenic. I'll keep checking.

[Full disclosure: I have been privileged to have collaborated scientifically with Sir Richard Roberts, one of the leaders of the group of Nobel Laureates who authored the letter on GMOs. I was not involved in the writing of that letter and I was unaware of it until it was published.]